Radially compliant acoustic line array hose

ABSTRACT

A radially compliant acoustic line array hose with improved toughness and wear resistance, suitable for use in towed acoustical line array sonars. The hose comprises a long extruded cylindrical tubing of a soft flexible grade of geophysical, plasticized polyvinyl chloride material with longitudinal ribs of a stiffer, harder grade of geophysical plasticized polyvinyl chloride material located at or near the tubing surface, and spaced uniformly around the circumference of the tubing. The ribs are melt-bonded to the softer thermoplastic material while each is in their respective melt stages during the extrusion process.

STATEMENT OF GOVERNMENT INTEREST

The invention described herein may be manufactured and used by or forthe Government of the United States of America for governmental purposeswithout the payment of any royalties thereon or therefor.

BACKGROUND OF THE INVENTION

The present invention generally relates to towed acoustic line arrayhoses and more particularly to a radially compliant towed acoustic linearray hose which provides improved wear resistance and toughness withoutsacrificing radial compliance and flexibility.

Prior acoustic line array hoses were fabricated of either an extrudedthermoplastic material or a composite of one or more cured elastomericcompounds reinforced longitudinally, and often radially, with highstrength fiber materials.

Extruded thermoplastic hose materials used are usually a flexible gradeof Polyvinyl Chloride (PVC) or Thermoplastic Polyurethane (TPU).Flexibility is required so as to obtain sufficient radial complianceassociated with low self-noise as well as satisfactory coiling andhandling characteristics at environmental temperatures. Line arraysonars with extruded outer tubing of PVC or TPU alone in thisflexibility range are not tough enough however to obtain an adequateservice life with desired reliability. The main damage mechanismscausing failure of the tubing envelope are abrasion, puncture by sharpobjects and cut-through at the edges of banding clamps and spacers. Suchfailures generally occur in service, particularly during deployment,handling and storage, thereby presenting a major reliability problem.

Reinforced elastomeric hoses, depending on the strength and orientationof the reinforcing fibers, while somewhat more resistant to bandingclamp and spacer cut-through, are subject to abrasion, nicks, cuts andsometimes punctures by sharp objects, have lower radial compliance andare limited as to the continuous length able to be produced by thepresently used mandrel-wrapping and curing process.

SUMMARY OF THE INVENTION

Accordingly, it is a general purpose and object of the present inventionto provide an improved toughness acoustic line array hose. It is afurther object that the device be high in reliability. Another object isthat the hose have high self-noise damping properties. An additionalobject is that the device be radially compliant to permit it to beeasily coiled for storage and handling purposes. Further objects arethat the hose exhibit improved abrasion, tear, cut and cut-throughresistance. These and other objects of the invention and the variousfeatures and details of construction and operation will become apparentfrom the specification and the drawings.

The above stated objects are accomplished with the present invention byproviding a co-extruded acoustic line array hose which combines theproperties of two or more thermoplastic materials in a manner where thedesirable properties of each material are utilized to maximum advantageand the drawbacks or less desirable characteristics are diminished. Aplurality of longitudinal runners of a tougher, stiffer thermoplasticare bonded to a softer, more flexible thermoplastic matrix. By varyingthe material properties, bonding methods and the size, shape, number,spacing and location of the tough runners, hose characteristics can betailored for specific applications. Because a continuous extrusionprocess may be used, previous hose length limits associated with mandrelwrapped fiber reinforced hoses are mitigated.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an acoustic line array hose section built in accordancewith the teachings of the present invention;

FIG. 2 is a sectional view taken along line 2--2 of FIG. 1; and

FIG. 3 is a block diagram representing the co-extrusion processaccording to the teachings of subject invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to FIG. 1 there is shown an acoustic line array hosesection 10 which comprises a long extruded cylindrical tubing 12 of asoft, flexible grade of geophysical plasticized polyvinyl chloridematerial with a plurality of longitudinal ribs 14 of a stiffer, hardergeophysical plasticized polyvinyl chloride material. FIG. 2 shows saidribs 14 located at or near the tubing surface and spaced uniformlyaround the circumference of the tubing. The longitudinal ribs 14melt-bond to the softer, flexible matrix material 12 during theextrusion process and are sized and spaced to function as a hard,abrasion-resistant surface which can withstand tearing, cutting andwearing when dragged over gravel or other sharp objects--particularlywhen the cutting edge moves perpendicular to the axis of the tubing.Said ribs 14 also resist cut-through at the edges of banding clamps andspacers thereby protecting the softer flexible material 12 between andbelow the stiffer ribs.

The flexibility and radial compliance of the tubing is provided byoptimizing the compliance and self-noise damping characteristics of thesofter thermoplastic material 12 between the ribs 14, thereby allowing amuch larger choice of materials for the hard longitudinal ribs 14.Compliance in a polymer is the dynamic ratio of strain amplitude tostress amplitude and as used herein applies in the radial direction.Damping refers to vibration attenuation with low damping materialshaving a typical damping factor of 0.1 and high damping materials havinga typical damping factor of 1.0. Self-noise for a towed array referspredominantly to the sound and vibration associated with hydrodynamiceffects produced by towing.

FIG. 3 shows the process whereby an acoustic line array hose 10 isco-extruded from a single extrusion die 16. The soft, flexible grade ofgeophysical, plasticized polyvinyl chloride material in the No. 1screwtype extrusion machine 18 is heated to above its melt temperatureand fed to die 16 through line 22 which connects extrusion machine 18 todie 16. Concurrently, the stiffer, harder grade of geophysical,plasticized polyvinyl chloride material in the No. 2 screwtype extrusionmachine 20 is heated to above its melt temperature and fed to die 16through line 24 which connects extrusion machine 20 to die 16. The twomaterials are then brought into contact within die 16 while still abovetheir respective melt temperatures, melt bond on a molecular scale alongthe interface surfaces of the different hardness materials andsubsequently harden by coling to form continuous acoustic line arrayhose 10.

What has thus been described is a type of acoustic line array hose whichcombines the properties of two or more thermoplastic materials in amanner where the desirable properties of each material are utilized tomaximum advantage and the less desirable characteristics are diminished.In one continuous tubing there are increased toughness, improvedabrasion, tear and cut-through resistance while at the same timeself-noise damping, radial compliance and flexibility characteristicsare retained. Using a co-extrusion process, thermoplastic materials thatwould otherwise not be compatible, can be combined during their meltstage thus forming a tenacious bond. The size, number and spacing of theexternal longitudinal ribs can be varied to meet the severity of theoperational environment commensurate with high damping, low self noiseand radial compliance. The flexible matrix material 12 of the hose canbe selected from many compositions of geophysical plasticized polyvinylchloride or thermoplastic polyurethane by choosing the one whoseproperties minimize array self-noise. The location of the ribs 14 on theouter surface can also be changed to a mixture of both outer and innersurfaces if internal components are thought to be a threat to hose wallintegrity.

The invention is further illustrated by the following examples:

EXAMPLE 1

A radially compliant acoustic line array hose with eight longitudinal,hard ribs was co-extruded using the teachings contained in thisdisclosure. A flexible grade of geophysical, plasticized polyvinylchloride with a hardness of 70-75 on the Shore `A` scale was selected asthe soft matrix material and a stiffer grade of the same material with aShore `A` hardness of 90-95 was chosen for the longitudinal ribs. Thesematerials were co-extruded at a temperature above their melt point,i.e., from 300°-350° F., and allowed to harden into a final hose sizeand shape as follows:

    ______________________________________                                        Outside Diameter (Flexible Matrix)                                                               1.1" (Nominal)                                             Wall Thickness (Flexible Matrix)                                                                 .1"                                                        Number of Ribs     8                                                          Rib Spacing        45° apart                                           Rib Shape          Elliptical                                                 Rib Size           .125" (Major Axis)                                                            .062" (Minor Axis)                                         Rib Location       On external hose circum-                                                      ference with major axis                                                       of the elipse tangent to                                                      the circumference and                                                         intersecting the circum-                                                      ference at the focal                                                          points of the elipse                                       ______________________________________                                    

EXAMPLE 2

A radially compliant acoustic line array hose was coextruded which wasidentical to the hose of Example 1 in all respects except that the softmatrix material used was a thermoplastic polyurethane with a Shore `A`hardness of 70-75.

It will be understood that various changes in the details, materials,steps and arrangement of parts which have been herein described andillustrated in order to explain the nature of the invention, may be madeby those skilled in the art within the principal and scope of theinvention as expressed in the appended claims.

What is claimed is:
 1. A line array hose comprising:a long cylindricaltube of soft, flexible thermoplastic material having high dampingcharacteristics for providing low self-noise and radial compliance assaid hose is towed through the water; and a first plurality of raisedlongitudinal ribs of a stiffer, harder thermoplastic material, bonded tosaid long cylindrical tube and spaced uniformly around the circumferencethereof at a predetermined distance from each other, for providing wearand cut-through resistance for said cylindrical tube in such a way as tomaintain said high damping characteristics and radial compliance.
 2. Aline array hose according to claim 1 wherein said long cylindrical tubematerial is a flexible grade of geophysical plasticized polyvinylchloride.
 3. A line array hose according to claim 1 wherein said longcylindrical tube material is a thermoplastic polyurethane.
 4. A linearray hose according to claims 2 or 3 wherein said first plurality ofraised longitudinal ribs material is a stiffer grade of geophysical,plasticized polyvinyl chloride, each said raised longitudinal rib beingmelt-bonded to the exterior surface of said long cylindrical tube.
 5. Aline array hose according to claim 4 wherein each of said firstplurality of raised longitudinal ribs has an elliptically shaped crosssection, said ribs being generally located on the exterior surface ofsaid long cylindrical tube such that the major elipse axis of said ribsis tangent to the exterior surface and intersects the circumferentialplane of said exterior surface at the focal points of said elipse, saidribs thereby being partially embedded in said hose so as to provide saidwear and cut-through resistance while also providing a low drag profileduring towing.
 6. A line array hose according to claim 5 wherein saidfirst plurality of raised longitudinal ribs comprises a quantity ofeight.
 7. A line array hose according to claim 5 wherein a secondplurality of raised longitudinal ribs are melt-bonded to the interiorcircumferential surface of said long cylindrical tube for providingcut-through protection to said hose against internal array components.8. A line array hose according to claim 7 wherein said second pluralityor raised longitudinal ribs comprise a quantity of eight.